This revised project will define the role of positive-acting virus-encoded chemokines and chemokine receptors as determinants of host cell trafficking that facilitate virus infection and dissemination in the host. During the past period, this grant supported the discovery and characterization of human CMV chemokine homologs (UL146 and UL147), demonstrating that one (UL146) is a functional chemokine (denoted vCXC-1) that attracts neutrophils via a specific interaction with the receptor hCXCR2. In addition, the murine CMV chemokine homolog, MCK-1, was shown to be a bone fide positive-acting chemokine that signals to macrophages and facilitates inflammation to attract cells for virus dissemination in the host animal. This proposal will focus on understanding how virus-encoded homologs of chemokines and chemokine receptors influence dissemination in the course of acute or latent infection. The first aim will be to study human CMV vCXC-1 (pUL 146) as a potential recruiter of host cells important in acute or latent infection. The impact of vCXC-1 on hCXCR2-bearing cell types will be investigated in cultured human and mouse cells as well as in mice by engineering vCXC-1 into the murine CMV genome. To model the behavior of human CMV, dissemination behavior will be evaluated in mice engineered to express hCXCR2 in the granulocyte-macrophage lineage, an approach that is possible because mice lack natural vCXC-1 responsive leukocyte populations. The second aim of this proposal will be to investigate the role of murine CMV MCK-2 in trafficking behavior of monocyte/macrophage cell populations. MCK-2 is a positively-acting, monocyte-attracting chemokine that influences a monocyte-associated viremia and influences inflammation and dissemination in mice. The aim will identify cell type(s) that respond to MCK-2 and that mediate viral dissemination by cell surface markers as well as by functional properties such as antigen presentation and immune clearance properties. Recombinant MCK-2 will be employed to identify the murine receptor(s) that recognize MCK-2. In order to determine the spectrum of modulatory functions carried out by MCK-2, animals and cells with a variety of immune and chemokine receptor defects will be employed to assess MCK-2 impact on the innate immune response to virus. The third aim of this proposal will be to investigate signalling and cell migration control via the human CMV US28 chemokine receptor, relying on a recombinant human and murine CMV, as well as cell lines expressing US28 in the absence of viral infection. Microarray analysis has shown that US28-expressing virus induces gene expression consistent with reorganization of cytoskeletal components and these will be dissected during the next grant period. The overall goals of the project will greatly increase the understanding of human CMV dissemination and pathogenesis critical to its success as a ubiquitous pathogen.